Industrial Pressure, Level, and Density Measurement is a practical, application-focused guide for technicians, engineers and students. Written clearly with real-world examples, this book begins with measurement fundamentals and explains how instruments convert physical quantities (such as pressure, level and density) into useful readings. It then covers pressure gauges, calibration principles and common pressure transducers, illustrating how accuracy, repeatability and calibration are established and maintained.

This Second Edition discusses modern transmitters and communication systems, including HART, Foundation Fieldbus and wireless options, and explains how digital transmitters improve diagnostics and system integration. Various level measurement techniques are explored, ranging from dipsticks and floats to ultrasonic, radar (both non-contact and guided-wave), capacitance, nuclear and hydrostatic head methods. Practical installation tips, such as managing turbulence, foam, coatings or solids, are also provided.

Finally, the text covers density measurement, hydrostatic tank gauging (HTG) and instrument selection and maintenance. It emphasizes selecting the appropriate technology for a specific process, considering environmental limitations, accuracy requirements and ownership costs. This is a practical, hands-on guide for anyone working with industrial measurement systems.

List of Illustrations xv
List of Tables xxvii
Preface xxix
About the Author xxxi

1 Introduction to Measurements 1

2 Pressure Measurement and Calibration Principles 7
2.1 Introduction 7
2.2 Fluid Properties Relating to Pressure Measurement 7
2.3 Standard Instruments for Calibration 37

3 Pressure Transducers and Pressure Gages 83
3.1 Introduction 83
3.2 Pressure Transducers 83
3.3 Pressure Elements 84

4 Transmitters and Transmission Systems 133
4.1 Introduction 133
4.2 Secondary Transducers 134
4.3 Potentiometers 135
4.4 Signal-Conditioning Circuits for Resistance Devices 136
4.5 Variable Inductance Transducers 141
4.6 Linear Variable Differential Transformer 142
4.7 Variable-Capacitance Transmitters 145
4.8 Electrical Strain Gage Transmitters 150
4.9 Resonant Frequency Transmitter 153
4.10 Silicon Resonant Sensor 158
4.11 Variable-Reluctance Transmitters 160
4.12 Piezoresistive Transmitters 164
4.13 Flapper-Nozzle Transmitters 165
4.14 Pneumatic Relay 168
4.15 Negative Feedback 170
4.16 Summary of Transmitter Types 172
4.17 Safety Transmitters 174
4.18 Differential-Pressure Measurement 176
4.19 Differential-Pressure Applications 179
4.20 Closed Tank Level Measurement by Differential Pressure 179
4.21 Flow Measurement by Differential Pressure 180
4.22 Industry-Standard Transmitters 184
4.23 The Dynamics of Pressure Transmitters 186
4.24 Digital Transmitters and Field Communication 187
4.25 Digital Transmitters 188
4.26 Improved Digital Sensors 188
4.27 Highway Addressable Remote Transducer (HART) 190
4.28 Digital Transmitter Operation 193
4.29 HHC Transmitter Smart Family Interface 200
4.30 Topology 202
4.31 Point-to-Point 202
4.32 Multidrop 203
4.33 Calibrating HART Field Devices 204
4.34 A HART Calibrator 205
4.35 Troubleshooting HART 208
4.36 HART Summary 212
4.37 Applications 222
4.38 Introduction to Wireless Communication 227
4.39 Specifications and Standards for Wireless Technology 228
4.40 Topologies 2314.41 Self-Organizing Networks 234

5 Level-Measurement Theory and Visual Measurement Techniques 245
5.1 Introduction 245
5.2 Visual Measurement Methods 247
5.3 Dipsticks, Lead Lines, Steel Tapes with Bobweights 247
5.4 Sight Glasses 249
5.5 Automatic Tank Gages 254
5.6 Magnetic-Type Float Devices 266
5.7 Magnetic Tank Gage 268
5.8 Displacement Principles for Level Measurement 270
5.9 Variable-Displacement Measuring Devices 270
5.10 Displacers Used for Interface Measurement 276
5.11 Field-Mounted Interface Controllers 278
5.12 Application of Displacer Actuated Level Controllers 282
5.13 Maintenance and Calibration 290
5.14 Multi-displacer Applications 292
5.15 Instrument Mounting and Special Applications 293

6 Hydrostatic Head Level Measurement 297
6.1 Introduction 297
6.2 Principle of Operation 297
6.3 Open-Tank Head Level Measurement 298
6.4 Hydrostatic Head Level Measurement 304
6.5 Diaphragm Box 304
6.6 Air-Trap Method 308
6.7 Air Purge or Bubble System 308
6.8 Head Level Measurement in Closed-Tank Applications and Pressurized Vessels 310
6.9 Mounting Considerations: Zero Elevation and Suppression 312
6.10 A Multivariable Level Controller 319
6.11 Diaphragm Seals 322
6.12 Summary of Diaphragm Seal Systems 324
6.13 Repeaters Used in Closed-Tank Level Measurement 325
6.14 Summary of Hydrostatic Head Level Measurement 326

7 Electrical Level Measurement 331
7.1 Introduction 331
7.2 Resistance Level Measurement 331
7.3 Capacitance Level Measurement 337
7.4 Capacitance Measurement Techniques 346
7.5 Application Considerations 352
7.6 Installation Considerations 353
7.7 Process Considerations 355
7.8 Material to Be Measured 355
7.9 Tank Construction Material 356
7.10 Tank Pressure and Operating Temperature 357
7.11 Humidity Changes 357
7.12 Material Agitation 357
7.13 Radio Frequency Admittance Level Measurement 357
7.14 Conductance Level Measurement 363
7.15 Sonic and Ultrasonic Level Measurement 363
7.16 Principle of Operation 364
7.17 Parasitic Echoes 370
7.18 Transducer-Related Parasitic Echoes 371
7.19 Secondary Echoes in Covered Tanks 372
7.20 Point Measurement 374
7.21 Noninvasive Ultrasonic Sensors 375
7.22 Summary—Ultrasonic Measurement 378
7.23 Radar Level Detection 378
7.24 Microwave Principle 380
7.25 Pulse Radar 380
7.26 Frequency Modulated Continuous Wave Radar 382
7.27 Signal Evaluation for FMCW Radar 382
7.28 Microwave Antenna 385
7.29 Contact and Non-Contact Operation 386
7.30 Tank Atmosphere 387
7.31 Temperature Sensors and Display Equipment 388
7.32 Applications 389
7.33 Floating-Roof Tank Installations (Pipe Installations) 389
7.34 Fixed-Roof Tank Installations 389
7.35 Liquefied Gas Installations 389
7.36 Tank Farm Storage and Waste Chemicals 389
7.37 Food Industry 390
7.38 Heavy Hydrocarbon Storage Vessels 391
7.39 Possible Interference Issues in Radar Level Measurement 391
7.40 End-of-the-Probe Algorithm 392
7.41 Interface Detection by Time Domain Reflectometry (TDR) 395
7.42 Summary—Radar Level Measurement 396
7.43 Fiber-Optic Liquid Level Measurement 398
7.44 Applications 399
7.45 Level Sensors for Refinery Vessels 399
7.46 System Configurations 400
7.47 Other Applications 401
7.48 Factors Affecting Index Measurements 403
7.49 Other Types of Level Measurement 403
7.50 Magnetostrictive Level Measurement 404
7.51 Nuclear Radiation Devices 407
7.52 Theory of Operation 407
7.53 Applications of Nuclear Radiation Level Measurement 409
7.54 Rotating Paddle 413
7.55 Vibration-Type Level Measurement 414
7.56 Thermal Level Measurement 415
7.57 Laser Level Measurement 417
7.58 Level Measurement by Weight 420
7.59 Mounting and Installation of Load Cells 420
7.60 Hydraulic Load Cells 422
7.61 Strain Gages 422

8 Liquid Density Measurement 427
8.1 Introduction 427
8.2 Units and Definitions Related to Density 427
8.3 Density Measurement by Hydrostatic Head 431
8.4 Displacer Density Measurement 436
8.5 Radiation Density Measurement 438
8.6 Radiation Source 440
8.7 Shielding 441
8.8 Radiation Detectors 441
8.9 Signal Conditioning 441
8.10 Density Gage Applications 442
8.11 Oscillating Coriolis Density Measurement 447
8.12 Summary of Coriolis Measurement 448
8.13 Ball-Type Density Meter 449
8.14 Capacitance-Type Density Measurement 449
8.15 Hydrometer 450
8.16 Vibrating Spool Density Measurement 453
8.17 Weight of Fixed Volume 454
8.18 U-Tube Density Gage 455
8.19 Insertion Liquid Density Measurement 457
8.20 Microwave Density Meter 458
8.21 Density Applications of Microwave Measurement 460

9 Hydrostatic Tank Gaging 463
9.1 Introduction 463
9.2 HTG Principles 463
9.3 Tank Calibration 464
9.4 Tank Calibration Methods 465
9.5 Tank Recalibration and Recomputation 472
9.6 Recalibration Guidelines 473
9.7 Recomputation Guidelines 475
9.8 HTG Measurements 477
9.9 Applications of HTG Technology 480
9.10 Vertical Cylindrical Tanks 480
9.11 Liquid Petroleum Gas (LPG) Tanks 480
9.12 Batch Processing 481
9.13 HTG Calculations 483
9.14 Calculating HTG Accuracy 486
9.15 HTG Assumptions and Level Calculation 487
9.16 HTG Assumptions and Gross Volume Calculation 488
9.17 HTG Assumptions and Mass Calculation 488
9.18 HTG Assumptions and Net Volume Calculation 489
9.19 Effect of Tank Geometry 489
9.20 Advantages and Limitations of HTG 490
9.21 New Developments and Trends 493
9.22 A Multi-function Tank Gage 495

10 Instrument Selection and Applications 505
10.1 Introduction 505
10.2 Summary of Pressure Applications 505
10.3 Summary of Level Applications 510
10.4 Summary of Solids Level Measurement 538
10.5 Radar Applications in Stilling Wells and Bypass Pipes 540
10.6 Head Level Measurement with Density Compensation 541
10.7 Summary of Density Compensation for Head Measurement 545
10.8 Conclusion—Level Measurement 545

Appendices

A Definition of Terms 551

B Deadweight Gage Calibration 575
B.1 Introduction 575
B.2 Calibration of Piston Gages by Crossfloat 576
B.3 Inspection of Weights 578
B.4 Calibration of Weights 578
B.5 Deadweight Gage Inspection and Preparation for Calibration 579
B.6 Preliminary Calibration Operations 580
B.7 Calibration of Piston Gages 582
B.8 Crossfloat Balancing With the Proximity Indicator 583
B.9 Test Report 589
B.10 Adjustments of Piston Pressure Gage Weights for a Specific Environment 590
B.11 Recalibration Interval for Hydraulic Deadweight Gages 593

C Pressure Instruments Form ISA-20.40a1 595

Answers to Exercises 597
Index 615